Make mine a whopper

'I was the guy who always got the crappy jobs - kinda ironic as I now have the coolest job ever invented. I feel it's time to pay my dues.'

Dressed in a comfy, loose-fit style that says 'half man, half sofa', amiable Texan Richard Linklater is just the kind of laid-back dude you'd expect to have directed School Of Rock (2003) and classic 1991 slacker movie, err, Slacker.

As we lazily chew the fat talking about books (he's a big Tolstoy fan), his farm upbringing in Houston, his 13-year-old daughter ('If she felt she had to work at McDonald's, I'd let her. I don't like to impose anything') and the nature of existence ('I prefer unreality. Reality can be a bummer'), you'd struggle to think of anyone who seems less like an 'activist'.

But Linklater has turned crusader with his latest film, Fast Food Nation. Based on journalist Eric Schlosser's best-selling 2001 exposé of America's junk food market, it's a stomach-churning abattoir-to-anus exposé of what makes your burger moo. So, what's his beef?

'I read the book like everyone else - and loved it. It's really about the machine taking over America. But I didn't see a movie there. Because I don't do documentaries,' lilts Linklater, gently drifting ever further towards the horizontal.

'But then I thought it's such an important subject matter and Eric had the idea to fictionalise it. That seemed more natural to me. It's not a documentary, it's not a satire, or a comedy... it's a realistic film about a world you're not meant to see or know about.'

Fair enough. Yet the self-taught director of last year's A Scanner Darkly - a boundary-pushing sci-fi deploying rotoscope animation - was never going to resist experiment.

Fast Food Nation emerges as a factional mish-mash of ensemble cast stories based around the mainly migrant, exploited menial workers all but enslaved into 'McJobs' at outlets and meat-processing plants.

The cast includes the tasty line-up of Avril Lavigne, Ethan Hawke and Little Miss Sunshine co-stars Greg Kinnear and Paul Dano. Plus Bruce Willis, in rare but brilliant baddie mode as an unrepentant cattle supplier who tells the hero: 'We all have to eat a little s*** from time to time.'

The result will make you think twice about biting into a Big Mac. Though Linklater, a believer in personal responsibility and choice, is hardly one to shove a message down your throat, the final footage - shot in a real slaughterhouse - will make even the most enthusiastic carnivore heave.